At the present time, respirators with double source of energy (electric and pneumatic), principaly used in hospitals, have an alarm system for signalirg malfunctions connected either directly with the operation of the respirator, or with physiological disturbances of the patient which prevent him/her from receiving the ventilation furnished by the respiratcr. This alarm system, most often actuated by a spirometer placed on the patient's breathing circuit, is electronic, the respirator being actuated electrically and/or pneumatically.
On the other hand, up to the present time, emergency respirators with single source of energy, used in ambulances, do not possess an alarm system. The reason for this resides in that, for this type of respirator, it is very important that the alarm system be entirely pneumatic.